Each year, the Permanent Service for Mean Sea Level (PSMSL) starts anew to
gather as much data as possible from the previous year to update the tide gauge
time series. For example, during 2013 we tried to update all time series
from active stations with the 2012 data. Other changes also occur to the
data set over the course of a year. In some cases, the yearly effort includes
the addition of new time series. Occasionally, data suppliers provide a
replacement time series for an existing record. Thus, changes to the data set
frequently reflect more than an addition of 12 monthly means. This update marks
an internal milestone as we start a new year and provides the best opportunity
to update our products.